There is a strong motivation to deploy the smart seat occupation sensor in the following applications:                a) Detection of a human being on a seat.        b) Differentiation of the human being on the seat from the weight, potentially replacing seat pressure sensor commonly used in vehicles today.        c) Differentiation of the baby or child on a seat from the weight or adult.        d) Minimizing the loss of lives of babies or disabled persons left in a car on the sun.        e) Detection of the humans or animals in the vehicle areas.        f) Aftermarket seat occupation detection integration, i.e. deployment of the innovative apparatus in the vehicle cabin after the manufacturing of the vehicle is finished, which is not possible with the state-of-the-art solutions.        
The primary motivation to address those problems is related to improving safety aspects by providing new features. Additionally, economic benefits will be introduced, e.g. by avoiding unnecessary air bag activation. Proposed technology offers an alternative to currently commonly used systems integrated in car seats with more features and with lower or same cost.
There is a need to enable differentiation between an object placed on a seat and the human being seating. Seat occupation is currently commonly detected by the pressure sensors integrated in the seat. Current solutions generally cannot easily differentiate between the child, adult, or object placed on a seat. This information may be used for safety belt alarm or air bag activation. Namely, airbag system may be switched on or off depending on whether there is a human or object on a seat. Furthermore, the airbag explosion could be adjusted depending on whether there is a child or an adult present. A child in a rear facing child seat, which is placed on the right front passenger seat, is in danger of being seriously injured if the passenger airbag deploys.
The health or even a life of a child or a disabled person left alone in the vehicle, either intentionally or inadvertently, can be endangered in case the temperature in the vehicle rises. The baby or child could suffocate due to the lack of oxygen in the cabin. On a typical summer day, the temperature inside a parked car can be up to 30° C. higher than the outside temperature. 75% of the temperature rise occurs within 5 minutes of closing the car and leaving it, 90% of the temperature rise occurs within 15 minutes. Dark colored vehicles reach slightly higher temperatures than lighter colored vehicles. The greater the area of glass in a car, the faster is the rise in temperature. Larger cars heat up just as fast as smaller cars. As the temperature rises, children begin to develop heat stress and also to dehydrate. Young children are more sensitive to heat than older children or adults and are at greater risk of heatstroke. There are the mortal cases on infants reported in real world. From 1998 to 2012 in USA, 559 child heatstroke deaths in vehicles, 288 (52 percent) happened after caretakers simply forgot they were there in car.
The state-of-the-art pressure sensors incorporated in the seat require a wired connection to the vehicle infrastructure. Hence, additional system integration efforts are required during manufacturing, in addition to the actual sensor cost. If the seats are not present in a vehicle, e.g. in case second or third row of seats was removed, there is no information about the presence of humans or animals. Ideally the information on human or animal presence should be available regardless of the seat infrastructure.
It was published in different scientific articles that microwave radar sensor, in the frequency range 3-30 GHz, may be used to detect the vital signs. Especially 2.4, 3-10, 24 and 60 GHz vital sign demonstrators have been publicly reported.
The following patents and patent applications published in last several years show the relevance of the topic and the state-of-the-art.
US 20120242492 A1, “Seat occupancy detection and display system”, treats seat occupation by weight detection from sensors integrated in the seat, and further analysis by signal processing.
U.S. Pat. No. 8,115,648 B2, “Seat occupancy sensor”, of IEE and BMW, proposes pressure sensing systems integrated in vehicle seats.
U.S. Pat. No. 6,026,340 A, “Automotive occupant sensor system and method of operation by sensor fusion”, of Robert Bosch GmbH, proposes combined ultrasonic and infrared sensors for seat occupation detection.
WO 2013007540 A1, “Seat heater and capacitive occupancy sensor combination”, of IEE, proposes the combination of seat heating system with capacitive sensors.
EP 2631113 A1, “Seat device and method for disposing seat occupancy sensor used therein”, of Fijukura Ltd, treats specific pressure sensor arrangements.
DE 102011056522 A1, “Industrial truck i.e. forklift, has occupancy sensor and seat belt buckle sensor connected with control unit, where control unit is separate controller for monitoring correct usage of safety belt and separated from vehicle control system”, of Unde Material Handling Gmbh, proposes sensor in safety belts as a means for seat occupancy detection.
WO 2011033360 A1, “Vehicle seat occupancy sensor”, of Toyota, considers pressure sensor arrangements.
WO 2013092946 A1, “Occupancy sensor for occupiable item e.g. seat or bed”, of IEE, introduces thermistor for heat based sensing.
DE 10131080 A1, “Optical seat occupancy sensor networks”, of Daimler Chrysler Ag, introduces optical network for seat occupancy detection.
U.S. Pat. No. 8,013,727 B2, “Device for detecting vehicle seat occupancy”, introduces electrical capacity sensors for seat occupancy.
U.S. Pat. No. 6,445,988 B1, “System for determining the occupancy state of a seat in a vehicle and controlling a component based thereon” relates to utilization of neural networks and different transducers.
U.S. Pat. No. 6,736,231 B2, “Vehicular occupant motion detection system using radar” introduces ultrasonic radar approach for determining seat occupancy by detecting the vital signs information. Its “radar” based system has two physically separated receivers of reflected ultrasound signals, and two units for further processing.
U.S. Pat. No. 6,104,293 A, “Warning system for detecting presence of a child in an infant seat” is based on warning to be issued by stopping the ignition of the car and intelligence in the infant seats.
DE 60125353 T2, “Seat occupancy recognition system” is utilizing safety belts as an occupancy sensor.